This application claims the benefit of German patent application 10012005.9 filed Mar. 11, 2000, herein incorporated by reference.
The present invention relates to a bobbin-winding device for a cheese-producing textile machine with a pivotably seated creel for holding a cheese, and a damping device connected with the creel and acted on magnetically.
With cheese-producing textile machines, for example automatic cheese winders whose bobbin-winding devices operate at winding speeds of up to 2,000 m/min, there is always the danger that strong vibrations of the creels will occur in the process of winding cheeses.
At the start of a bobbin winding operation in particular, as well as in the course of producing very dense cheeses, there is the danger that the amplitude of the creel vibrations becomes so large that the winding process is negatively affected whereby cheeses may be produced which can barely be unwound and are therefore useless. For this reason, the known high-performance bobbin winding machines typically have a device for damping the creel vibrations.
A creel damping device for a bobbin winding machine which has a linearly operating hydraulic damping cylinder is described, for example, in German Patent Publication DE 195 34 333 A1. The damping element in this case is embodied as an oil damper and is connected via a lever to the creel.
Any leakage of the damper oil along the piston rod of these known damping devices is prevented by means of a seal. Since this seal continuously presses against the moving piston rod and therefore causes considerable static friction, a quite large breakaway torque must always be overcome before the damper moves. Since this breakaway torque occurs in both directions, the contact force between the cheese and the yarn guide drum which drives the cheese by means of a frictional connection is not unequivocally defined by the creel compensation means and can therefore not be set accurately.
Moreover, with known oil dampers there is always the danger that damper oil will leak, which leads to soiling of the surroundings, as well as to an impairment of the damping capability, which is not always immediately noticed.
Most of the past attempts to address these problems have proposed to replace these oil dampers by other damping devices. Swiss Letters Patent 374 003, for example, describes a damping device in which a hydraulic damping cylinder is replaced by an electromagnet, which can be charged with current and acts on an armature plate. The armature plate itself is connected via a rod with the creel to be damped. Thus, with this known damping device a force component is generated by means of an electromagnet, which presses the armature plate connected with the creel against a stationary abutment. Accordingly, the damping action of this damping device results from the mechanical friction between the armature plate and the abutment.
Since the damping device in accordance with Swiss Letters Patent 374 003 also has several grave disadvantages, this known damping device was also never able to gain acceptance in actual practice.
The damping device in accordance with Swiss Letters Patent 374 003 also necessitated a relatively large breakaway torque upon every actuation for displacing the armature plate in relation to the electromagnet, so that a defined creel compensation was hardly possible. Moreover, the wear which occurs in connection with this device is not inconsiderable, because the components performing the damping function are in mechanical contact.
In view of the above mentioned prior art, it is an object of the present invention to provide a damping device for the creels of high-performance textile machines which avoids the disadvantages of the known damping devices.
In accordance with the present invention, this object is addressed by a bobbin-winding device for a cheese-producing textile machine comprising a pivotably seated creel for holding a cheese, a damping device connected with the creel, and a stationarily arranged magnet system for generating a magnetic field. In accordance with the invention, the damping device has a movable electrically-conductive component at least indirectly connected with the creel and arranged to intersect the magnetic field of the stationarily arranged magnet system in a contactless manner.
More specifically, the movable electrically-conductive component preferably is embodied as a rotatable non-ferromagnetic damper disk an edge area of which is orthogonally penetrated by the magnetic field of the magnet system and therefore reacts almost free of hysteresis but also has the particular advantage of being almost free of wear since it operates in accordance with the so-called eddy current principle. That is, free electrons in the material of the disk in the range of the magnetic field of the magnet system are radially accelerated in the course of the appropriate rotation of the damper disk at an increased angular velocity, so that a circular current is generated in the disk plane.
This circular current generates a magnetic field, which enters into a reciprocal action with the magnetic field of the magnet system which penetrates through the disk. The torque created in the course of this action is proportional to the angular velocity, and its direction is always opposite the direction of movement of the damper disk. Thus, a contactless braking torque is generated by the eddy currents at the damper disk and is transmitted to the creel, where it automatically results in the effective damping of the occurring vibrations.
In a preferred embodiment, the magnet system is embodied as a permanent magnet system, because a device designed in this manner does not require any external energy supply.
Since the braking torque which can be achieved is not a function of the velocity with which the damping disk is moved through the magnetic field of the magnet system, the damping disk is furthermore connected to the creel by means of a gear mechanism. The gear mechanism provides the transmission of the angular velocity of the creel, so that the damper disk moves through the applied magnetic field at an angular velocity which clearly lies above the corresponding angular velocity of the creel.
Preferably, the damping disk is either made of aluminum or of copper. Both materials have a high degree of electric conductivity and therefore favor the generation of eddy currents.
In a preferred embodiment, the gear mechanism is embodied as an interlocking gear mechanism, preferably as a toothed gear mechanism, and has at least one gear wheel which is connected with the pivot shaft of the creel in a manner fixed against relative rotation, as well as a second gear wheel which is arranged on the damping disk also in a manner fixed against relative rotation. The gear wheels which mesh with each other transmit the vibration occurring in the area of the creel during winding operations with almost no delay to the damper disk, and also immediately return the braking torque initiated at the damping disk to the creel.
The gear ratio of the gear mechanism preferably lies between 3:1 and 10:1, optimally about 6:1. The angular velocity of vibrations, which can occur during the winding process at the creel, is transferred at a corresponding amplification to the damping disk by means of this gear ratio and thereby generates a corresponding, oppositely directed torque which is proportional to the angular velocity of the damper disk. This damping torque is transmitted back to the creel via the gear mechanism and in the process is again amplified by the gear ratio factor of the gear mechanism. Thus, the gear ratio factor of the gear mechanism is effectively squared into the damping constant.
In order to always create a transmission gear which is almost free of play, it is preferred that the damping disk, or the gear wheel, which is arranged fixed against relative rotation on the damping disk, is rotatably seated via a bearing shaft on a rocker, on which a spring element acts such that the gear wheels of the gear mechanism are radially pushed against each other and therefore always mesh with each other free of play. In this manner, it is assured that it is possible to also transmit and dependably dampen creel vibrations of relatively low amplitudes.
In a preferred embodiment form, the creel is supported in a stationary console and is rotatable to a limited degree.
The permanent magnet system is preferably constructed in a U-shape and consists, for example, of a cuboid permanent magnet, as well as two laterally adjoining yoke elements made of a ferromagnetic material. The edge area of the damper disk moves in a contactless manner between these two yokes, which results in good bundling of the magnetic field of the permanent magnet.
In an alternative embodiment, the permanent magnet system can also have several permanent magnets whose polarization are respectively arranged such that the magnetic flux is conducted several times in different directions through the damping disk.
The spacing of the yokes from each other is preferably matched to the thickness of the damper disk and is selected such that as narrow as possible an air gap is formed between each of the yokes and the damping disk.